Reduction of Other Functional Groups by Hydride Donors

Reduction of Other Functional Groups by Hydride Donors 

One experimental test for the involvement of radical intermediates is to study 5-hexenyl systems and look for the characteristic cyclization to cyclopentane derivatives (see Part A, Section 11.2.3). When 5-hexenyl bromide or iodide reacts with LiAlH4, no cyclization products are observed. However, the more hindered 2,2-dimethyl-5-hexenyl iodide gives mainly cyclic product.164 

Some cyclization also occurs with the bromide, but not with the chloride or the tosylate. The secondary iodide, 6-iodo-l-heptene, gives a mixture of cyclic and acyclic product in THF.165 

Reduction of Carbon-Carbon Multiple Bonds, Carbonyl Groups, and Other Functional Groups 

The occurrence of a radical intermediate is also indicated in the reduction of 2-octyl iodide by LiAlD4 since, in contrast to the chloride or bromide, extensive racemization accompanies reduction. 

CHAPTER 5 REDUCTION OF CARBONYL AND OTHER FUNCTIONAL GROUPS 

NaBH3CNa l-Iodododecane, HMPA, 25°C, 4h l-Dodecyl tosylate, HMPA, 70°C, 8h 

One experimental test for the involvement of radical intermediates is to study 5-hexenyl systems and look for the characteristic cyclization to cyclopentane derivatives (see Section 

Epoxides are converted to alcohols by UAIH4. The reaction occurs by nucleophilic attack, and hydride addition at the less hindered carbon of the epoxide is usually observed. 

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Scheme 5.7. Reduction of Other Functional Groups by Hydride Donors... 

Reduction of other functional groups by hydride donors... 

Conversion of a carboxylic acid to a thiohydroxamate ester, followed by heating the product in the presence of a suitable hydrogen donor such as tri-n-butyltin hydride, produces a reductive decarboxylation. This sequence of reactions is called the Barton decarboxylation reaction and may be used to remove a carboxylic acid and replace it with other functional groups. 

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